1. School of Advanced Materials and Nanotechnology Xidian University 266 Xinglong, Section of Xifeng Road Xi'an 710126 P. R. China
2. Shaanxi Key Laboratory of High‐Orbits‐Electron Materials and Protection Technology for Aerospace(HMP) Xidian University 266 Xinglong Section of Xifeng Road Xi'an 710126 P. R. China
3. Electronic Materials Research Laboratory (Key Lab of Education Ministry) State Key Laboratory for Mechanical Behavior of Materials and School of Electronic Science and Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China
4. School of Physics Xi'an Jiaotong University Xi'an 710049 P. R. China